Check manual page of citrix_controller.registered
Citrix Controller: Desktop Registered
This check outputs the number of desktops currently registered to a
Citrix XenApp 7.x controller. The citrix_farm.ps1 plugin must be
installed on the controller, and the Check_MK agent must be executed
with Citrix Admin permissions for this to work. This check is purely
informative and always OK.
One service per controller is created.